Yes, Puppy has a good letter for that.. I thought he posted that here for you already?
Remove the "open" in your relationsip description... the meaning is NOT what you want to convey... you don't want an "open" relationahip by current standards of the term...
You also need to rephrase this "choose him or me" thing
You arne't after your wife to choose between two men.. SHE thinks that's the problem.. It's NOT
You want your wife to choose between
a. Exploring reconcilliation b. Destroying her family and her marriage
THAT is the choice being made, NOT between YOU and this OM... Don't ENABLE this nonsense like that...
EDUCATE HER as you write... don't word things in HER fantasy mindset... this is NOT some hollywood movie.. There are CHILDREN here that are going to get HURT